The invention relates to a radiation source, and in particular a source of radiation in the ultraviolet or extreme ultraviolet spectral range.
One field of application of the invention relates to the production of ultraviolet radiation which is used in the production of integrated circuits by means of lithography.
The increase in the density of integration of integrated circuits necessarily leads to a reduction in the dimensions of the constituent parts thereof.
It is thus desirable to produce circuits which have constituent parts having dimensions of less than 70 nanometres by using ultraviolet radiation sources and this has resulted in the need to reduce the wavelength of the ultraviolet radiation produced by the sources to lower values of, for example, 13.5 nanometres.
There are a number of types of source which can emit in the extreme ultraviolet range: synchrotron sources, sources of radiation produced by laser and sources produced by electrical discharges.
The document “Spectroscopic and energetic investigation of capillary discharges devoted to EUV production for new lithography generation” by Eric Robert, Branimir Blagojevic, Rémi Dussart, Smruti R. Mohanty, Moulay M. Idrissy, Dunpin Hong, Raymond Viladrosa, Jean-Michel Pouvesle, Claude Fleurier and Christophe Cachoncinlle, “Emerging Lithographic Technologies V, Proceedings of SPIE” Vol. 4343 (2001) describes a source of radiation in the extreme ultraviolet range, by means of electrical discharges.
The discharge is produced between an anode and a cathode in a space which is filled with gas. The discharge energises the gas molecules which emit radiation in order to become de-energised.
One of the disadvantages of the discharge radiation sources is the low quantity of energy which they radiate.